Re: [PATCH 07/32] acpi-video-detect: Rewrite backlight interface selection logic

From: "Pali Rohár" <pali.rohar@gmail.com>
To: Hans de Goede <hdegoede@redhat.com>
Cc: Darren Hart <dvhart@infradead.org>,
	"Rafael J. Wysocki" <rjw@rjwysocki.net>,
	Ben Skeggs <bskeggs@redhat.com>,
	Azael Avalos <coproscefalo@gmail.com>,
	Corentin Chary <corentin.chary@gmail.com>,
	Lee Chun-Yi <jlee@suse.com>,
	Cezary Jackiewicz <cezary.jackiewicz@gmail.com>,
	Matthew Garrett <mjg59@srcf.ucam.org>,
	Ike Panhc <ike.pan@canonical.com>,
	Anisse Astier <anisse@astier.eu>,
	Mattia Dongili <malattia@linux.it>,
	Henrique de Moraes Holschuh <ibm-acpi@hmh.eng.br>,
	platform-driver-x86@vger.kernel.org,
	ibm-acpi-devel@lists.sourceforge.net,
	acpi4asus-user@lists.sourceforge.net,
	dri-devel@lists.freedesktop.org, Aaron Lu <aaron.lu@intel.com>,
	linux-acpi@vger.kernel.org
Subject: Re: [PATCH 07/32] acpi-video-detect: Rewrite backlight interface selection logic
Date: Thu, 11 Jun 2015 11:19:22 +0200	[thread overview]
Message-ID: <20150611091922.GB19820@pali> (raw)
In-Reply-To: <1433941292-21530-8-git-send-email-hdegoede@redhat.com>

On Wednesday 10 June 2015 15:01:07 Hans de Goede wrote:
> Currently we have 2 kernel commandline options + dmi-quirks in 3 places all
> interacting (in interesting ways) to select which which backlight interface
> to use. On the commandline we've acpi_backlight=[video|vendor] and
> video.use_native_backlight=[0|1]. DMI quirks we have in
> acpi/video-detect.c, acpi/video.c and drivers/platform/x86/*.c .
> 
> This commit is the first step to cleaning this up, replacing the 2 cmdline
> options with just acpi_video.backlight=[video|vendor|native|none], and
> adding a new API to video_detect.c to reflect this.
> 
> Follow up commits will also move other related code, like unregistering the
> acpi_video backlight interface if it was registered before other drivers
> which take priority over it are loaded, to video_detect.c where this
> logic really belongs.
> 
> Signed-off-by: Hans de Goede <hdegoede@redhat.com>

Hello,

lot of people are using acpi_backlight parameter in kernel cmdline to
fix some of problems. I would like to see this parameter still working
and to not break existing configuration. E.g acpi_backlight=vendor to
use dell-laptop.ko or thinkpad_acpi.ko backlight.

It is still nightmare to get laptop panel backlight working on different
(broken) laptops and people learnt to try to use acpi_backlight
parameter for quit/hot fixing these problems. Upgrading kernel (if you
remove acpi_backlight parameter) just break it again.

-- 
Pali Rohár
pali.rohar@gmail.com
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